sorry my answer solved for y not x. y = xy^2 + 0.5x^2 + c. i'm 99.9% sure that dy/dx is therefore y^2 + x . For a basic guide to calculus go here http://www.tlchm.bris.ac.uk/~paulmay/misc/1s/calcl t3.htm
or type basic calculus into any search engine
Trouble is, you need to differentiate y wherever it appears. So in your answer, you need to differentiate y on the left side of the equation (which you did), and also on the right side of the equation where it appears as y^2 (which you didn't).